Oil and Gas Seepage in the Ocean: Contributions to the Sedimentary and Dissolved Organic Carbon Pools

Naturally occurring gas and oil seepage is a widespread phenomena in many parts of the world ocean especially in continental margin sediments. Its significance to methane production and accumulation associated with gas hydrate formation has been well documented. However, a little is known about the potential importance of oil and gas seepage to the sedimentary organic carbon (SOC) and dissolved
organic carbon (DOC) pools in the deep ocean.
In a recent cruise (August, 2000) to Green Canyon (680m), Gulf of Mexico, we collected sediment and water samples around seepage areas during dives of the research submersible Johnson Sea-Link. SOC, DOC, fluorescence, stable carbon isotope and hydrocarbon concentrations were measured for these samples. Our results suggest that the gas and oil seepage could be potential sources contributing
'old' carbon to both SOC and DOC pools in the deep ocean in this area. Approaches for assessing the long term influence and importance of oil and gas seepage to global oceanic carbon cycling will be discussed.